The so-called scalable encoding signifies the encoding technology such that from single encoding data, one part thereof is cut out, and its cut-out encoding data is decoded, thereby enabling decoded images each having a different resolution, frame rate and bit rate to be generated. The scalable encoding allows a processing cost of the encoding, a accumulating cost, and a cost for the processing prior to delivery to be reduced more remarkably than preparing the encoding data independently for terminals each having a different reproduction environment, and transmission environments. Also in an MPEG, being an encoding technology of the International Standard, the scalable encoding technology has been established simultaneously with the technology of encoding the single moving picture. And, the technology of performing the encoding with high efficiency also has been proposed in this scalable encoding technology (for example, Patent document 1).
FIG. 7 is a block diagram signifying a configuration of the moving picture encoding device having the scalable encoding technology of performing the encoding with high efficiency, being the foregoing prior art. An operation of the moving picture encoding device having the prior art will be explained by employing FIG. 7.
The moving picture encoding device shown in FIG. 7 encodes two input image signals 1000 and 2000 each having a different resolution.
An encoder 20 encodes the input image signal 2000 of a smaller resolution (hereinafter, referred to as a low hierarchy), and generates texture information encoding data 2001 and motion information encoding data 2999. Simultaneously therewith, the encoder 20 outputs a decoded image signal 2002 that is obtained by decoding these items of encoding data. A filter 199 enlarges the decoded image signal 2002 so that it has a resolution identical to that of the input image signal 1000 of a greater resolution (hereinafter, referred to as a high hierarchy), and outputs an enlarged decoded image signal 2003. An encoder 11 makes a reference to the enlarged decoded image signal 2003 to encode the input image signal 1000, and generates texture information encoding data 1002 and motion information encoding data 1999.
The encoder 20 is an encoder for encoding the image signal of a single resolution that is used conventionally, and for example, the moving picture encoder that is specified by the MPEG is employed for it.
The encoder 11 is comprised of a frame memory 100, a motion estimation unit 101, a motion compensation unit 102, a filter 104, a texture conversion unit 105, a texture encoding unit 112, a texture inverse conversion unit 106, and a motion information encoding unit 107. Hereinafter, a configuration and an operation of the encoder 11 will be explained in details.
The frame memory 100 having the decoded image signal filed that is obtained by, after having encoded the input image signal 1000 input in the past, decoding it. The motion estimation unit 101 makes a reference to a decoded image signal 1005 filed in the frame memory 100 and the enlarged decoded image signal 2003, thereby to generate motion information 1998 signifying how each region within the input image signal 1000 behaves for these reference signals. The motion compensation unit 102 subjects the decoded image signal 1005 and the enlarged decoded image signal 2003 to motion compensation processing according to the motion information 1998, and generates a prediction signal 1007 of the input image signal 1000. Subtracting the prediction signal 1007 from the input image signal 1000 allows a prediction error signal 1001 to be generated. The texture conversion unit 105 subjects the prediction error signal 1001 to frequency conversion and quantization. The texture encoding unit 112 encodes quantization conversion coefficient information 1012 that the texture conversion unit 105 outputs to generate texture information encoding data 1002. The motion information encoding unit 107 encodes the motion information 1998 to generate motion information encoding data 1999. The texture inverse conversion unit 106 subjects the quantization conversion coefficient information 1012 to inverse quantization and frequency inverse conversion to output a decoding prediction error signal 1003. Adding the decoding prediction error signal 1003 and the prediction signal 1007 allows a decoded image signal 1004 to be generated. The decoded image signal 1004, which is filed into the frame memory 100, is employed as a reference signal of the motion compensation at the time of encoding the other frames of the input image signal 1000.
Making a reference to a decoding result of the low-hierarchy image signal in addition to the past frame already encoded in encoding the high-hierarchy image signal makes it possible to encode it more efficiently. For example, encoding a difference with the decoding result of the low-hierarchy image signal in the region that was obscured due to a shadow of a body in the past frame and has come out for the first time in the present frame makes it possible to encode the image signal with high efficiency than performing the motion compensation prediction having a correlativity in the temporal direction taken into consideration.
Patent document 1: JP-P2001-320715A